1. Field of the Invention
This invention relates to a head-up display optical film, a head-up display, and a vehicle.
2. Background Art
Head-up display (HUD) displays various traffic information through the windshield of a vehicle such as a car and an aircraft on the external background field. In such a head-up display, 3-4% reflection at each air-windshield interface on the inside and outside of the windshield doubles the projected image and deteriorates visibility.
There is a solution of providing a anti-reflection layer on the outside interface of the windshield to decrease the outside reflectance resulting in the suppression of double image. However, it is ineffective when a water layer is formed on the low-reflection layer, for example, in rainy weather.
On the other hand, U.S. Pat. No. 7,158,059B2 proposes a method of using a half-wave plate to cause S-polarized light to be incident on the windshield at Brewster's angle. However, it has a problem in that the image is invisible to a user wearing a polarized sunglass that does not transmit S-polarized light.